Intraoperative evaluation of ischemic colitis presents several problems related to diagnosis, severity, and extension. The aim of this study was to determine the usefulness of photopletysmography (PPG) to detect colonic arterial wave amplitude changes in patients operated on for ischemic colitis, comparing the affected area with a control area on the transverse colon. Four patients were studied, two with gangrenous colitis, and two with protracted "transient" ischemic colitis. All four patients survived. PPG is a useful method for intraoperative diagnosis and surgical assessment of ischemic colitis.